Flexible band drive



g- 1966 E. J. HUNKELER 3,267,812

FLEXIBLE BAND DRIVE Filed July 22, 1964 5 Sheets-$heet 1 FIG. 2

INVENTOR. ERNST J. HUNKELER AZTTORNEY g 23, 1965 E. J. HUNKELER3,267,812

FLEXIBLE BAND DRIVE 5 Sheets-Sheet 2 Filed July 22, 1964 g 23, 1965 E.J. HUNKELER FLEXIBLE BAND DRIVE 5 Sheets-$heet 3 Filed July 22, 1964FIG. 4

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r n 3,267,812 Patented Aug 1966 3,267,812 FLEXIBLE BAND DRIVE Ernst J.Hunkeler, Fair-port, N.Y., assignor to The Gleason Works, Rochester,N.Y., a corporation of New York Filed July 22, 1964, Ser. No. 384,331

12 Claims. (Cl. 90-5) The present invention relates to flexible band ortape drives such as are employed in gear generating machines fortransmitting motion between a slide and a rotary drum or sector intangential relation thereto.

The primary objectives of the invention are to increase theload-carrying capacity of such drives without increasing the dimensionsof the bands, and to eliminate or at least substantially reduce unwantedoscillations or vibrations in the drive system.

A drive according to the invention comprises a sector supported forangular motion, a member supported for motion tangentially of thesector, flexible bands anchored to said sector and to said member fortransmitting motion between them as though they were rolling together innonslip relation, and means for exerting pressure between said sectorand member to effect a friction drive between them supplementary to thepositive drive through said bands.

The foregoing and other objects and advantages will appear from thefollowing description of the preferred embodiment of the invention shownin the accompanying drawings, wherein:

FIG. 1 is a drive diagram of a bevel gear generating machineincorporating the improved drive;

FIG. 2 is a detail sectional view taken approximately in plane 22 ofFIG. 3;

FIG. 3 is a front view of the drive including the sector, bands andadjacent parts;

FIGS. 4 and 5 are detail sectional views, approximately in planes 4-4and 55 of FIG. 3; and,

FIGS. 6 and 7 are side and front views of a modified drive.

The drive shown in FIG. 1 is applicable to bevel gear generatingmachines, such for example as that shown in my co-pending applicationSerial No. 354,048, filed Mar. 23, 1964. The drive, effected by aunidirectionally rotating motor-driven shaft 1, rocks a tool-carryingcradle 2 back and. forth about its axis 3 and in time therewith rotatesa work spindle 4 back and forth about its axis 5. The cradle issupported by a frame 6, FIGS. 25, which also supports a housing in whichspindle 4 is journaled. The frame also supports, either directly orindirectly, the other elements of the drive, including shaft 1.

A cam 7 on shaft 1 acts on a follower 8 on a lever 9 to rock the latterabout its fulcrum 11 to the frame. A block 12 manually adjustable on thelever, to vary its distance from the fulcrum, is pivoted to a block 13that is slidable in a transverse guide slot 14 in a slide 15. This slidehas bearings 16 slidable on cylindrical rail 17 of a guide 18 supportedby the frame. Flexible steel bands 19 and 21 are anchored by screws 22to the slide and by band-tensioning devices 23 to a sector 24. Thissector is angularly adjustable on the cradle 2, for this purpose beingsecured thereto by screws 25 anchored in a circular T-slot 26 in theface of the cradle, concentric of axis 3. The sector is so-calledbecause the part of its surface contactable by the bands is confined tothe are between anchorages 23. The sector of course may be a completecircular drum if so desired. The band-contacting surface of the sector,designated 27, is cylindrical and coaxial of axis 3; the band-contactingsurface 28 of the slide 15 is plane and parallel to guide rail 17. Asshown in FIG. 2, the side bands 19, which act to drive the cradle 2during rotation clockwise in FIGS. 1 and 3, are each approximately halfthe width of the center band 21 which acts to drive the cradlecounterclockwise.

A hearing portion 29 of slide 15 slidably supports a parallel slide 30that is connected to slide 15 by a lever 31 fulcrumed to the frame at32. The lever is pivoted to a block 33 that is slidable in a cross-slot34 in slide 30. A similar block 35, slidable in a cross-slot 36 in slide15, is pivoted to a block 37 that is adjustable on the lever 31 to varyits distance from fulcrum-32. A re-circulating ball nut 38 non-rotatablysecured to slide 30 is threaded onto a screw 39 which constitutes a partof a shaft 41. This shaft is journaled for rotation and constrainedagainst axial motion in the frame, so that upon reciprocation of slide30 the shaft 41 is rotated back and forth. Shaft 41 drives the workspindle 4 through ratio-of-roll change gears 42, gears 43, differentialgear set 44, 45, 46, bevel gears 47, 48, 49 and 51, and worm and wormwheel 52 and 53, the latter being on the work spindle. The angle throughwhich the cradle 2 is oscillated during each turn of the cam 7 may bevaried by adjustment of block 12 on lever 9, while the ratio of angularmotion of the cradle to angular motion of the work spindle 4 may beadjusted coarsely by change of gears 42 and finely by adjustment ofblock 37 on lever 31.

Indexing of the work spindle, to bring successive tooth slots of a workgear into cutting position, is effected by a mechanism 54 whose outputshaft 55 carries the planet gear 45 of differential set 44-46. Themechanism 54, which may be hydraulically operated, is controlled by avalve 56 actuated by a cam 57 on shaft 1. 'By this arrangement indexingoccurs once for each turn of shaft 1 and earn 7. The angular position ofcam 57 on shaft 1 determines whether such indexing will occur at areversal point of the rotation of the cradle or during the course ofcradle rotation in one direction or the other.

On each side of bands 19, 21, FIG. 2, the slide 15 has plane surfaces 58parallel to guide rail 17 and adapted for frictional drive contact withcylindrical surfaces 59 on sector 24. Preferably these surfaces 58 and59 are respectively aligned with the neutral or medial planes of theportions of the bands parallel to slide 15 (rail 17) and with theneutral or medial cylinders of the portions of the bands on thecylindrical surface 27. Accordingly these surfaces 58 and 59 whenpressed together constitute frictional drive surfaces which tend totransmit motion between the slide and sector in substantially the samevelocity ratio as the motion positively transmitted by the bands.

Pressure for the friction drive is provided by a compression spring 61,FIG. 5, which acts between a pintle 62 supported by a two-part bracket63 on the machine frame 6 and a plunger 64 which is slidable in acylinder bore in the bracket and bears against the guide 18. The latteris guidingly supported for motion toward and away from the sector 24 byflanges 65 on bracket 63 and by a pivot 66, FIGS. 3 and 4, secured tothe frame 6. This arrangement accommodates manufacturing tolerances inthe concentricity of sector 24 and in the bearings of slide 18 and ofcradle 2. The pressure exerted by the spring is adjustable by means of ascrew 67 disposed between bracket 63 and pintle 62. In a typical machineembodying the invention this pressure is such that the friction drivebears the major portion of the total drive load between the slide andsector, the bands serving primarily to maintain the intended phaserelation between these elements. However if desired the pressure may bereduced so that the friction drive will bear only a minor portion of thetotal drive load, and serve primarily for damping vibrations oroscillations in the hand drive.

Primarily to avoid the possibility of first-and-last tooth spacingerror, by causing the band and friction drive to cooperate in as nearlyas possible the same manner when cutting every tooth slot of a workgear, means are provided to release the spring pressure between surfaces58 and 59 just prior to each tooth slot cutting cycle. These meanscomprise a cylinder chamber 68, between plunger 64 and bracket 63, towhich hydraulic pressure is applied by valve 56 at the same time thatthis valve causes the index mechanism 54 to operate. Hydraulic pressuremay also be applied manually by means of a valve 69, to release thespring pressure between surfaces 58 and 59 while the machine is beingadjusted, particularly when an angular adjustment between the cradle 2and the sector 24 is being made.

Preferably the surfaces 58, 59 and the surfaces 27, 28 are so relatedthat the spacing of the latter is slightly greater than the thickness ofthe bands 19, 21, so that slight variations in this thickness will notaffect the friction drive between surfaces 58, 59. If desired, thesurfaces 58, 59 may be omitted so that the friction drive resulting fromthe pressure of spring 61 (or equivalent pressure means) will be throughsurfaces 28, 27 and the bands. In this event it is preferred that therebe a slight clearance between surfaces 27 and 28 and the inner band 21,so that the friction drive will be exclusively through the outer bands19.

For the purpose of stabilizing the slide 15, a guide 71 is secured tothe machine frame 6 beneath the overhanging bearing portion 29 of theslide. A follower 72 on the slide slidably contacts surfaces 73 of thisguide, which are parallel to guide rail 17.

The modification illustrated in FIGS. 6 and 7 is useful for transmittingmotion between two angularly oscillating members, instead of between anangularly oscillating member and a reciprocating member.

In this modification, two sectors 74 and 75, which are really completedrums, are mounted for reversing rotation respectively in machine frame76 and in a guide 77 which is pivoted to the frame at 78. Pressuremeans, comprising a piston 79 bearing against the guide and a cylinder81 secured to the frame, act to press cylindrical surfaces 82 and 83 ofthe sectors into frictional drive contact when hydraulic pressure isapplied to the cylinder through conduit 84. Flexible steel bands 85 and86, secured to the sectors by anchorages 87, are arranged to positivelytransmit angular motion between the sectors in substantially the samevelocity ratio as motion transmitted by friction drive through surfaces82, 83.

Having now described preferred embodiments of my invention, and theirmode of operation and use, what I claim is:

1. A drive comprising a sector angularly movable on a support, a membermovable tangentially of the sector on a guide which is movable relativeto the support to displace said member toward or away from the sector,flexible bands anchored to said sector and to said member fortransmitting motion between them as though they were rolling together innon-slip relation, and means for exerting pressure between the supportand the guide to press said member and sector together and therebyeffect a friction drive between them supplementary to the positive drivethrough said bands.

2. A drive according to claim 1 in which said pressure exerting meansare arranged to exert said pressure in a direction substantiallyperpendicular to the plane of tan- .gency of said sector and bands.

3. A drive according to claim 1 in which said sector and member havefrictionally engageable surfaces for transmitting motion between them insubstantially the same ratio as that transmitted by said bands, saidsurfaces being maintained in frictional drive contact by said pressuremeans.

4. A drive according to claim 3 in which the neutral stress portions ofsaid bands are substantially aligned with said frictionally engageablesurfaces.

5. A drive according to claim 4 in which there is a pair of suchfrictionally engageable surfaces on each side of the bands.

6. A drive according to claim 1 in which said member is a slidesupported for rectilinear motion on said guide.

7. A drive according to claim 6 in which said guide is pivoted to thesupport.

8. A drive according to claim 1 in which said member is a sectorsupported for angular motion in said guide.

9. A gear machine having a frame supporting for angular motion thereon awork spindle and a tool-carrying cradle, a generating train connectingthe cradle and spindle for rotation back and forth about theirrespective axes, actuating means for said generating train, said trainhaving indexing means therein operable by said actuating means foreffecting an angular advance of the work Spindle during each cycle ofsaid back and forth rotation, said generating train including a sectorsecured to the cradle, a slide reciprocable on the frame tangentially ofthe sector, flexible bands anchored to the sector and to the slide fortransmitting motion between them as though they were rolling together innon-slip relation, said slide and member having frictionally engageablesurfaces for transmitting motion between them in substantially the sameratio as that transmitted by said bands, pressure means acting betweenthe frame and slide for pressing the slide against the sector tomaintain said surfaces in frictional drive contact, and means operableby said actuating means for effecting a release of such pressure duringeach cycle of said back and forth rotation.

10. A drive comprising a sector supported for angular motion, a membersupported for motion tangentially of the sector, flexible bands anchoredto said sector and to said member for transmitting motion between themas though they were rolling together in non-slip relation, and meanscomprising a spring for exerting pressure between said sector and memberto effect a friction drive between them supplementary to the positivedrive through said bands, and means for releasing said pressure.

11. A gear machine having a drive in the generating train thereofcomprising a sector supported for angular motion, a member supported formotion tangentially of the sector, flexible bands anchored to saidsector and to said member for transmitting motion between them as thoughthey were rolling together in non-slip relation, and means for exertingpressure between said sector and member to effect a friction drivebetween them supplementary to the positive drive through said bands;actuating means for oscillating said drive and for intermittentlyindexing a work gear on the machine in time with such oscillation; andmeans operable by said actuating means in time with such oscillation forreleasing said pressure.

12. A drive comprising a sector supported for angular motion, a membersupported for motion tangentially of the sector, flexible bands anchoredto said sector and to said member for transmitting motion between themas though they were rolling, together in non-slip relation, and meanscomprising a fluid pressure device for exerting pressure between saidsector and member to effect a friction drive between them supplementaryto the positive drive through said bands, and means for releasing saidpressure.

References Cited by the Examiner UNITED STATES PATENTS 842,416 1/1907Nelson 74--95 X 1,160,368 11/1915 Bozell et a1.

(Other references on following page) 5 6 UNITED STATES PATENTSReferences Cited by the Applicant 12/1925 Stebbins 74--108 X FOREIGNPATENTS 11 1927 Ph 4-209 451940 g i Z4401 150,283 7/1921 Great Britain.9 1950 Johnson 4 95 X 5 501,097 2/1939 Great Britain. 4/1963 Rieckenberg74-95 FOREIGN PATENTS 10/1963 France.

9/1935 Italy.

BROUGHTON G. DURHAM, Examiner.

10 D. H. THIEL, Assistant Examiner.

FRED C. MATTERN, ]R., Primary Examiner.

1. A DRIVE COMPRISING A SECTOR ANGULARLY MOVABLE ON A SUPPORT, A MEMBERMOVABLE TANGENTIALLY OF THE SECTOR ON A GUIDE WHICH IS MOVABLE RELATIVETO THE SUPPORT TO DISPLACE SAID MEMBER TOWARD OR AWAY FROM THE SECTOR,FLEXIBLE BANDS ANCHORED TO SAID SECTOR AND TO SAID MEMBER FORTRANSMITTING MOTION BETWEEN THEM AS THOUGH THEY WERE ROLLING TOGETHER INNON-SLIP RELATION, AND MEANS FOR EXERTING PRESSURE BETWEEN THE SUPPORTAND THE GUIDE TO